1. Field of the Invention
The present invention relates to a suspension system of a vehicle and more particularly to a device having the function of a fluid dynamic damper for damping relatively low frequency vibrations of the vehicle, particularly in the fore-and-aft direction.
2. Description of the Prior Art
It is well known that a suspension system of an automotive vehicle consists of suspension rods each of which is adapted to connect a member on a wheel side to a member on a vehicle body side. Each suspension member is provided with a solid rubber bushing thereby to damp vibration transmitted from the wheel side to the vehicle body side.
However, such a suspension system is so arranged to achieve damping of the vibration input from the road wheel side to the vehicle body side only by the damping action of the rubber bushing itself. Accordingly, in the case the suspension system resonates at the frequency of the input vibration, the vibration supression action on a vehicle body is unavoidably deteriorated, thereby lowering damping function of the suspension system.
In view of the above shortcomings, in the case such a conventional suspension rod is used in a front suspension system, so-called harshness phenomena is caused by vibrations at 10 Hz to 40 Hz which are transmitted to the vehicle body from the wheels during vehicle cruising on an uneven paved road or like, thus increasing noise within a passenger compartment. Additionally, in the case such a conventional suspension rod is used in a front suspension system, vibrations at the frequencies lower than 20 Hz are transmitted to a steering system thereby to cause so-called shimmy phenomena, thus deteriorating steering stability.